All Tests

Electromyography (EMG) is a diagnostic procedure that evaluates the health condition of muscles and the nerve cells that control them. These nerve cells are known as motor neurons. They transmit electrical signals that cause muscles to contract and relax. An EMG translates these signals into graphs or numbers, helping doctors to make a diagnosis.

A doctor will usually order an EMG when someone is showing symptoms of a muscle or nerve disorder. These symptoms may include tingling, numbness, or unexplained weakness in the limbs. EMG results can help the doctor diagnose muscle disorders, nerve disorders, and disorders affecting the connection between nerves and muscles.

There are two components to an EMG test: the nerve conduction study and needle EMG. The nerve conduction study is the first part of the procedure. It involves placing small sensors called surface electrodes on the skin to assess the ability of the motor neurons to send electrical signals. The second part of the EMG procedure, known as needle EMG, also uses sensors to evaluate electrical signals. The sensors are called needle electrodes, and they are directly inserted into muscle tissue to evaluate muscle activity when at rest and when contracted.

During each part of the EMG procedure, one electrode releases a very mild electrical signal while the other electrodes measure how long it takes for the signal to reach them. This mimics the natural electrical signals sent by the nerves to the muscles. The distance between the electrodes and time it takes for a signal to reach them is used to determine the speed at which the nerves are able to send and receive signals. An abnormal speed usually indicates a muscle or nerve disorder.